1. Field of the Invention
2. Description of the Related Art
This invention relates to a firing mechanism for a pyrotechnic flare signalling device.
Known firing mechanisms have a hollow casing with an opening formed at one end, the casing being adapted to be fitted by said one end to a pyrotechnic flare signalling device so that the opening is aligned with ignition means of pyrotechnic means of the pyrotechnic flare signalling device. A firing pin is located within the casing and means operable when the pyrotechnic flare signalling device is fitted to said one end of the casing to thrust the firing pin through the opening to impact the ignition means and actuate the pyrotechnic means, said means that are operable to thrust the firing pin through the opening upon manual release of a trigger mechanism.
If the trigger mechanism has to be cocked by pulling a cocking lever before it can be operated to cause the firing pin to be thrust through the opening, there is a risk of misfiring due to the cocking lever having not been pulled down fully or of inadvertent firing when the mechanism has been cocked.
An object of this invention is to minimise the risk of misfiring or of inadvertent firing.
According to one aspect of this invention there is provided a firing mechanism for a pyrotechnic flare signalling device, the firing mechanism having a hollow casing with an opening formed by one end, the casing being adapted to be fitted by said one end to the pyrotechnic flare signalling device so that the opening is aligned with ignition means of pyrotechnic means of the pyrotechnic flare signalling device, a firing pin within the casing and means operable when the pyrotechnic flare signalling device is fitted to said one end of the casing to thrust the firing pin through the opening to impact the ignition means and actuate the pyrotechnic means, said means that are operable to thrust the firing pin through the opening, including an energy storage device, means operable to load the energy storage device, releasable catch means operable to hold the energy storage device in a loaded condition and releasable to cause or allow release of energy by said energy storage-device whereby to generate the thrust that thrusts the firing pin through the opening, a plunger slidably mounted within an axially extending chamber which is formed by the interior of the casing, said releasable catch means being operable to hold the plunger against movement towards said opening and releasable to free the plunger for movement towards said opening, and a trigger mechanism which is adapted to be actuated to release said catch means and allow said plunger to be urged towards said opening by release of energy by said energy storage device, wherein the plunger is rotatable about its axis within a cylindrical portion of the chamber as well as being axially slidable therein, the releasable catch means including a stop member which is carried by the casing and which is adapted to be abutted by an abutment on the plunger when the plunger is in one angular orientation relative to the casing whereby to stop axial movement of the plunger towards said opening, said plunger being formed so as to bypass said stop member when the plunger is displaced angularly from said one angular orientation relative to the casing so that said abutment is displaced angularly with respect to said stop member and the plunger is free to slide towards the opening past the stop member, said trigger mechanism including means operable to rotate the plunger after said energy storage device has been loaded to a certain extent whereby the abutment is displaced angularly with respect to the stop member with further loading of the energy storage device.
Preferably the plunger is a slave plunger and the trigger mechanism includes a master plunger slidably mounted in tandem with the slave plunger within said axially extending chamber, resilient means which act between the plungers to oppose reduction of a gap between them, the master plunger being movable towards the slave plunger and thereby to compress the resilient means when the slave plunger is held by the catch means, and catch release means which are adapted to be actuated to release said catch means by advancement of said master plunger to a certain location relative to the slave plunger, the arrangement being such that, after an initial advance of the master plunger towards the slave plunger which compresses said resilient means, said catch means are released and said slave plunger is urged towards the opening by expansion of the resilient means whereby to generate the thrust that is applied to the firing pin.
Conveniently the means operable to rotate the slave plunger are means on the master and slave plungers which are adapted to interact so that axial displacement of the master plunger is converted into angular displacement of the slave plunger. The means on the master and slave plungers may be axially aligned spiral ramp surfaces, the spiral ramp surface on the master plunger being brought into face to face contact with the spiral ramp surface on the slave plunger as the master plunger arrives at said certain location, further linear advance of the master plunger towards the opening causing the spiral ramp surface on the slave plunger to slide on the spiral ramp surface of the master plunger so that the slave plunger is rotated about its axis. The portions of the master and slave plungers that face one another may be tubular, the end of each tubular portion that faces the tubular portion of the other plunger forming a diametrically opposed pair of such spiral ramp surfaces.
In a preferred embodiment, the slave plunger has a slot formed in it, the slot forming a lateral aperture that extends through the slave plunger from side to side, the slot being elbow shaped and having a laterally extending portion and an axially extending portion, the laterally extending portion being at the end of the axially extending portion that is nearer to said opening, the laterally extending portion and the axially extending portion of the slot forming a shoulder at the end of the laterally extending slot portion remote from the opening, that shoulder serving as said abutment, and said stop member comprising a pin which extends through the slot and which is anchored at its end in the casing on either side of the slave plunger. The edge of the laterally extending portion of the slot that forms said abutment may extend substantially radially with respect to the slave plunger. Furthermore the edge of the laterally extending slot portion that is nearer to said opening may be oblique to the axis Of the slave plunger so that the laterally extending slot portion diverges away from the axially extending slot portion.
The tubular portion of the slave plunger may be closed at its end nearer to said opening, the slave plunger carrying a reduced diameter probe portion which projects towards said opening. The end of the reduced diameter probe portion of the slave plunger may have a dished recess formed therein.
Preferably the firing mechanism includes means limiting the stroke of axial movement of the slave plunger and of the firing pin such that they are spaced one from the other even when the slave plunger is closest to the firing pin, wherein a gravity responsive element is provided and arranged to assume a rest position between the slave plunger and the firing pin when the casing is upright for firing with the opening at the top and the slave plunger is below the firing pin but above the master plunger, the dimensions of the gravity responsive element being such that it can be raised from its rest position and moved into contact with the firing pin by the slave plunger whereby the thrust is transmitted from the slave plunger to the firing pin through the gravity responsive element when the casing is upright for firing whereas it would be displaced from between the slave plunger and the firing pin when the casing is not upright so that thrust cannot be transferred from the slave plunger to the firing pin. This arrangement has the advantage that the flare signalling device can only be fired when the firing mechanism is upright so that it is unlikely to be usable as an offensive weapon.
Conveniently the gravity responsive element is spherical and is located in a dished recess which is concave to the firing pin and which is formed by said casing, there being an axially extending passage which extends from the center of the recess towards the slave plunger to receive a portion of the slave plunger which is slidable therein. Resilient biassing means which urge said slave plunger away from said opening may be provided.
According to another aspect of this invention there is provided a firing mechanism for a pyrotechnic flare signalling device, the firing mechanism having a hollow casing with an opening formed at one end, the casing being adapted to be fitted by said one end to the pyrotechnic flare signalling device so that the opening is aligned with ignition means of pyrotechnic means of the pyrotechnic flare signalling device, a firing pin which is constrained for rectilinear movement within the casing and means operable when the pyrotechnic flare signalling device is fitted to said one end of the casing to thrust the firing pin through the opening to impact the ignition means and actuate the pyrotechnic means, said means that are operable to thrust the firing pin through the opening including an energy storage device, means operable to load the energy storage device, releasable catch means operable to hold the energy storage device in a loaded condition and releasable to cause or allow release of energy by said energy storage device whereby to generate the thrust that thrusts the firing pin through the opening, and a trigger mechanism operable to release the catch means, the trigger mechanism including a plunger which is slidably mounted within an axially extending chamber which is formed by the interior of the casing, said releasable catch means being operable to hold the plunger against movement towards said opening and releasable to Free the plunger for movement towards said opening, means limiting the stroke of axial movement of the plunger and the firing pin within the casing such that they are spaced one from the other even when the plunger is closest to the firing pin, said trigger mechanism being adapted to be actuated to release said catch means and allow said plunger to be urged towards said opening by release of energy by said energy storage device, wherein a gravity responsive element is provided and arranged to assume a rest position between the plunger and the firing pin when the casing is upright for firing with the opening at the top and the plunger below the tiring pin, the dimensions of the gravity responsive element being such that it can be raised and moved into contact with the firing pin by the plunger whereby the thrust is transmitted from the plunger to the firing pin through the gravity responsive element when the casing is upright for tiring whereas it will be displaced from between the plunger and the firing element when the casing is not upright so the thrust cannot be transferred from the plunger to the firing pin.